* Electronegativity: Chlorine is highly electronegative, meaning it has a strong tendency to attract electrons towards itself. This is due to its position on the periodic table.

* Electron Configuration: Chlorine has 7 electrons in its outermost shell, and it wants to achieve a stable octet (8 electrons) configuration. By gaining one electron, it can achieve this stable state.

How Many Electrons?

Chlorine typically gains one electron to form a chloride ion (Cl-). This is because gaining one electron completes its outermost shell and makes it more stable.

Example: When chlorine reacts with sodium (Na), sodium loses one electron to become Na+ and chlorine gains that electron to become Cl-. This forms the ionic compound sodium chloride (NaCl).